PROJECT ABSTRACT This project will develop and pilot a brief, novel personal values-based intervention for promoting adherence to endocrine therapy (daily anti-hormonal medication) among breast cancer survivors. Endocrine therapy (ET) represents the most powerful way to prevent recurrence of the most common form of breast cancer (estrogen receptor-positive)1,2, cutting recurrence rates by 40-50%3,4, and breast cancer survivors who adhere to it live longer5,6. Although ET is generally prescribed once daily for five to ten years7,8, only half or fewer breast cancer survivors adhere to it as recommended6,9,10. Yet a recent Cochrane review11 identified no effective medication adherence interventions that were sustainable for community settings and found that only 1 of 182 trials focused on a cancer population, revealing a lack of disseminable approaches to promote ET adherence. By developing a low-cost, disseminable intervention to improve ET adherence, this project addresses this vital need11,12. In addition to educating patients on ET benefits and encouraging them to discuss side effects with providers, the proposed intervention innovatively links the medical value of ET adherence with patients' personal values (who and what are most important to them). Using piloted prompts to elicit values linked to taking ET, we will create a sticker with an image that captures each patient's top value (e.g., photo of grandkids, family, travel) and have patients attach this sticker to their ET medication box, creating an affective visual cue for promoting ET adherence. The intervention thus aims to create more positive and meaningful associations with ET, addressing a core set of risk factors for ET non-adherence13. Values comprise a central component of a theory-driven model for promoting behavior change and reducing psychological distress14,15, which we adapted to reduce distress among cancer survivors16 and which has been applied to change multiple health behaviors17-21. We propose to conduct the first study that applies values to improving ET medication adherence. The pilot will be conducted in collaboration with a statewide community oncology pharmacy, readying it for dissemination. We aim to: (1) Develop and refine the brief values intervention in response to patient (n = 10) and medical team (n = 5) feedback; (2) Conduct a pilot randomized trial (n = 80) among breast cancer survivors recently prescribed ET to preliminarily evaluate whether the values intervention (plus ET education), improves ET adherence (with electronic pillbox monitoring as primary outcome), positive and negative emotional associations with ET, and intentions to adhere to ET in the next 1 and 5 years, compared to an education-only control, and to assess intervention acceptability and evaluate the feasibility of a large-scale trial; (3) Revise intervention content in response to participant feedback, analyze data, and use findings to inform next steps. Given the life-extending benefits of ET5,6 coupled with the lack of brief, sustainable interventions designed to promote ET adherence11 the development, refinement, and piloting of this intervention has the potential to benefit both breast cancer survivors and the healthcare system. !